201-6 The Subsurface of Mars: Science Priorities and Access

Session: The G.K. Gilbert Award Session: Geology of Mars, Mercury, Asteroids, and Icy Satellites in Honor of Scott Murchie

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The subsurface is likely Mars’ longest-lived habitable environment that could host ancient biosignatures of past life or even extant microbial life. It could become accessible to exploration within the coming decade with proposed missions like Mars Life Explorer (MLE)(NASA), Tiawen 3 (China) and ExoMars Rosalind Frankin (ESA). Here we consider 3 aspects of subsurface exploration on Mars and address the driving science questions: 1) the crustal environment and subsurface architecture of Mars over meters to kilometers; 2) the nature of subsurface volatiles and transport pathways; and 3) implications for habitability of the Martian subsurface.

The upper crustal environment of Mars sets a key boundary condition for many key geological processes important to the subsurface.  Key questions include what is the physical structure of the crust within the upper crust and how does that contribute to porosity, permeability? What is the thermal state of the subsurface and the surface heat flow (temperature gradient, thermal conductivity)?  The NASA InSight mission has put rigorous constraints on key properties of the crust, including thickness, layering, porosity, density and inhomogeneities.  At the InSight landing site, porosity in the top-most layer is likely at least 5% to explain the measured low velocities. Two crustal seismic discontinuities detected at the InSight landing site near 8 km and 22 km depth could indicate the depth of viscous pore closure and/or different compositions of crustal layers.  The nature of subsurface volatiles is equivocal (e.g. is a diversity of thought on the characteristics of a cryosphere in the upper 8 km of the crust), yet enormously important. Geologic processes like impact cratering and faulting have exposed near surface ices while others expose deep sections of the Martian crust and have provided tantalizing clues to subsurface processes. The MARSIS and SHARAD orbital measurements rover-based GPR on Zhurong and Perseverance rovers have opened exciting directions linking surface observations to subsurface properties. Modeling of subsurface fluid flow has led to valuable insights into fluid flow in the crust, with much more opportunities to refine the models by incorporating quantitative orbital and rover data. The continued analysis of spacecraft data and planned missions of NASA, ESA and China in the next decade will contribute significantly to our understanding of the subsurface.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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